My dissertation research is focused on achieving a molecular and genetic understanding of human autosomal recessive polycystic kidney disease (ARPKD) and to then convert that understanding into a strategy for effective therapy. ARPKD is an inherited disease that is caused be mutations at the polycystic kidney and hepatic disease 1 (PKHD1) gene locus on chromosome six. Infants with ARPKD develop enlarged polycystic kidneys, dilatation of the renal collecting duct, and pulmonary hypoplasia, a result of oligohydramnios. Affected infants typically do not survive beyond one month due to renal and/or respiratory failure. The later childhood phenotype of ARPKD is characterized by cystic growth in the kidney and liver, accompanied by hepatic fibrosis. My research objective is to elucidate the physiological role for the PKHD1 gene product, polyductin, and to understand how mutations in PKHD1 result in the clinical manifestations of ARPKD. To this end I have focused on characterizing the expression, regulation, and function of polyductin, the PKHD1 gene product. Using a combination of cell biological, biochemical, and genetic approaches, I am assessing the function of polyductin and polyductin-like proteins in zebrafish and cells, using both knockdown and overexpression models. My specific aims are as follows. 1) To characterize the function of polyductin, the gene product of the ARPKD gene, in zebrafish. I have identified a zebrafish homolog of the pkhdl-like (pkhd1-l) gene that is believed to function in the same manner as the human PKHD1 gene. I have employed a reverse genetics approach towards understanding the function of pkhd1-l in zebrafish. Preliminary results from knockdown studies indicate that polyductin-L, the protein product of pkhd1-l, may function in a pathway that is shared with other ciliary proteins. The resultant phenotype from this knockdown is shared with other related PKD mutants and includes: kidney cysts, left-right axis defects, body curvature, and edema. 2) To characterize the function and trafficking of polyductin in the pathogenesis of ARPKD. In this aim I will characterize human polyductin expression in stable over- expressing cell lines. This study will examine the mechanisms of polyductin regulation, including post- translational modifications, cleavage, protein trafficking, and protein interactions. [unreadable] [unreadable] [unreadable]